Problem with HET 6904

Problem with HET 6904
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Problem with HET 6904 - 3/5/2008 9:19 AM

torecho

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Last Login: 4/14/2008
From: , SPAIN
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Hello,

I still haven't maiden my F-20 since I've been waiting to receive a new power plant:
EVO 22 3.700 4S1P - HET 2W-20 - Tsunami 72 - HET
6904.

I was going to test and measure the trhust yesterday night, and when testing the fan at half
throtle before assembling it on the plane, the impeler slipped away (lucky it didn't hit me)
flying against the wall, damaging one blade a little.

I've been reading several forums but ...

quote:

What I meant by that is the bore of the two aluminum pieces inserted into the impeller
is not 100% aligned with the bore of the impeller itself, so in order to be able to get the
collet to go smoothly into the hole I had to make a quick pass with the drill bit to clear
out the hole. Then it's just a matter of mounting the motor so the front of it is centered
and make sure that the impeller is balanced.

Or I don't understand it, or it is not what happens to me.

..I've opened a little the bore where the impeler allen screw (the head of the screw) inserts,
since it was not wide enough, and tightened the screw really hard (thought it was perfect).

What can I do?
(I have the bungee as well and I'm desperate for the maiden this weekend)

Thank You

< Message edited by torecho -- 3/5/2008 9:20 AM >

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RE: Problem with HET 6904 - 3/5/2008 8:07 PM

OldFart1

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(without power), spin the impeller rotor, and look to see if it's centered. easiest way I've found is to look at the distance from impeller to EDF housing in several spots around the circumference - it should be even (and shouldn't change as the rotor is slowly turned by hand).

If that checks out, do a slow run up, feeling for vibration.

If it fails (and it sounds like you have a one setscrew adaptor), try loosening the adaptor and turning the rotor on the motor shaft 1/8 of a turn at a time.

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Jeff/LAX

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RE: Problem with HET 6904 - 3/6/2008 8:34 AM

torecho

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The problem is solved. What happened was that the center bore was not big enough for the bolt, this is why it didn't 'hold' the shaft hard enough.

Roberto.

Thanks for replying Jeff.

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RE: Problem with HET 6904 - 3/6/2008 11:42 AM

CTulanko

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Good luck Roberto...keep us up to date on your maiden! Also, make sure you have around 25lbs of pull on the bungee...it takes a bit more than normal to get it airborne.

Best wishes,

Carl

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RE: Problem with HET 6904 - 3/6/2008 5:05 PM

OldFart1

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Was waiting to see if Carl would reply - as far as this plane goes, Carl is THE MAN!

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RE: Problem with HET 6904 - 3/6/2008 7:54 PM

torecho

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Thank You very much Carl. Thank you Jeff.

I'll let you know which is the lucky pinecone that receives the visit of my F-20.

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RE: Problem with HET 6904 - 3/10/2008 12:38 PM

torecho

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I'm desperate.
Everything ready, perfect thrust, bungee ready too.
Range test: At only five meters there was so mach glitching that I even had to unplug the battery.

I have checked everything, disassembled everything again,
-unsoldered the bec from the main bat cables, and used a aditional battery for it.
-removed the fan and connected the ESC I had before (with which I hadn't had any problem)
-Tried other batteries.
-Changed the receiver (trying the f-20 in other models, and other model's in the f-20)
-Taken the aerial out of the plane.
-Tried it without the esc connected (only with bec's batt and bec and the servos)

I AM FRUSTRATED.

< Message edited by torecho -- 3/10/2008 12:42 PM >

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RE: Problem with HET 6904 - 6/28/2009 1:32 AM

Mach9

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I have an HET F-20 glitch master. I spent many hours with many combinations of radio equipment including FM(PPM) & PCM with crystals and also synthesized. I tried two different transmitters and several frequencies. I also tried inside my house, outside and at two different fields. I tried with and without the motor connected, with and without the speed control connected. I tried multiple servos and connectors. Servos and connectors can cause glitching. I tried different batteries. I also tried filter capacitors. That is a LOT of combinations to test!! The PCM did a fair job but I would not trust it. The Corona synthesized receiver worked...let me explain. The Corona is crap because it has a very low resolution. The zero point deadband is sloppy so any glitches were ignored. I actually flew with this thing! It is the same as driving a car with the steering worn out where you have to constantly move the steering wheel to keep the vehicle straight. This was my first flight with an EDF jet and the first time this jet had flown! I fly with the fan hanging out...a propeller. I was very fortunate to land with the wings flopping back and forth. I had a pucker factor of 100! I am guessing the resolution to be something like 256 steps instead of 1024. The receiver I like best is the Castle Creations Berg. It is small, light and full range unlike PCM and it has fail-safe unlike FM. I do NOT recommend a standard FM receiver. Without fail-safe the motor can go nuts! My ESC is behind the motor in the duct. I read where the motor wires can be long and the battery wires should be as short as possible to prevent glitching so I considered moving the speed control since it has a high enough current rating it would not need super cooling. I did not move it because in my opinion that does not make sense with the battery producing pure DC and the motor output being pulsed. OK, this is long and everyone wants the answer. I could not find any way to stop the glitching with the antenna inside the airframe. It now hangs out the back between the duct and frame looking very stupid and works perfectly. I hope this solves a lot of problems for other people. If someone knows a way to make it work with the antenna inside, PLEASE let me know!!

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